The High Energy cosmic-Radiation Detection (HERD) facility has been proposed as a space cosmic-ray and gamma-ray detector, which will be installed on the China Space Station around 2027. HERD will be able to measure proton and nuclei fluxes up to the cosmic ray knee region (about 1 PeV), electron + positron flux up to tens of TeV and gamma rays above 100 MeV. The CALO, a homogeneous and 3D segmented calorimeter, is the core detector of HERD. It consists of about 7500 LYSO cubes with 3 cm side length, corresponding to about 55 radiation lengths (X0) and 3 nuclear interaction lengths for centrally incident particles in any
irection. The fluorescence light produce by each LYSO cube is read out using two independent systems. The first one uses wavelength shifting fibers to deliver the light to Intensified scientific CMOS(IsCMOS) cameras, whereas the second one makes use of photo-diode sensors. Both systems feature a dynamic range larger than 10E7. In this paper we will report the status of the CALO hardware and Monte Carlo simulation tudies on its performance.